1. Technical Field
The present invention relates in particular to a travel control apparatus for a vehicle capable whereby another vehicle in front in the same lane can be passed by automatic travel technology.
2. Related Art
In recent years, various devices have been developed and proposed in which automatic driving technology is used in a vehicle so as to allow a driver to perform safe and pleasant driving. For example, Japanese Unexamined Patent Application Publication (JP-A) No. 2009-248892 discloses a travel control system, in which the suitability of passing a preceding vehicle is determined by a vehicle equipped with the travel control system on the basis of a traveling state of the vehicle and the preceding vehicle. When it is determined that passing of the preceding vehicle is suitable, a passing preparations operation is performed. Then when it is recognized, on the basis of the travel environment and traveling state of the vehicle and the preceding vehicle, for instance, that the vehicle and the preceding vehicle are traveling along on a lane of a road having multiple lanes in each direction, there are no traffic lights and/or intersections or the like within a predetermined distance range in front, there are no other preceding vehicles in the passing path, and there is no following vehicle which might enter into the passing path, it is determined that passing of the preceding vehicle is possible, and passing is performed.
According to the technology of the travel control system according to JP-A No. 2009-248892, passing is performed in accordance with the travel environment (presence/absence of intersections and traffic lights), and preceding vehicles in the passing path, when the vehicle is seeking to perform a passing maneuver, and therefore it is possible to achieve a safe passing maneuver. However, passing a preceding vehicle which is the target of passing involves performing a complex combination of driving operations, such as lane changing in order to implement passing, accelerating after lane changing and lane changing back to the original lane after the acceleration for passing. Due to the traveling state of a following vehicle and a parallel traveling vehicle that is traveling in a lane that is adjacent to a lane to which the subject vehicle performs lane changing to pass the vehicle to be passed and is located on the opposite side of the lane in which the vehicle to be passed is traveling, there are cases where, for instance, it is desirable not to perform the passing maneuver, or where it is desirable to return to the original lane without passing the preceding vehicle, even after lane changing for passing, or and the passing maneuver must be performed by predicting these situations accurately.